Load drive control device

Abstract

A load drive control device is provided, which includes a pulse generator for generating pulse signals with a duty ratio to drive an inductive load, a feedback setting section for setting the duty ratio for feedback, a detection setting section for setting the duty ratio for detection of a natural vibration frequency of the inductive load, a natural vibration frequency setting section for setting the natural vibration frequency of the inductive load based on an actual current value detected at setting the duty ratio for detection, and a selection section for selecting the feedback setting section as a duty ratio setting section at a normal time and for selecting the detection setting section as the duty ratio setting section when a condition for detecting the natural vibration frequency is satisfied.

What is claimed is: 
     
       1. A load drive control device for controlling driving of an inductive load, the load drive control device comprising:
 a switching section provided in an energizing path of the inductive load, the switching section flowing an electric current to the inductive load when the switching section is ON; 
 a pulse signal generating section for driving the inductive load by generating pulse signals with a duty ratio at a drive frequency and by supplying the pulse signals to the switching section, wherein the drive frequency is predetermined; 
 an actual current value detection section for detecting an actual current value of the inductive load; 
 a feedback setting section for setting the duty ratio for feedback based on a deviation between a target current value of the inductive load and the actual current value detected by the actual current value detection section so that the actual current value follows the target current value; 
 a drive frequency setting section for setting the drive frequency of the pulse signals; 
 a detection setting section for setting the duty ratio for detection, the duty ratio for detection being provided for detecting a natural vibration frequency of the inductive load; 
 a natural vibration frequency setting section for setting the natural vibration frequency of the inductive load based on the actual current value that is detected when the duty ratio for detection is set; and 
 a selection section
 for, at a normal time when a predetermined condition for detecting the natural vibration frequency is not satisfied, selecting the feedback setting section as a duty ratio setting section, which sets the duty ratio in the pulse signal generating section, and 
 for, when the predetermined condition for detecting the natural vibration frequency is satisfied, selecting the detection setting section as the duty ratio setting section, which sets the duty ratio in the pulse signal generating section, 
 
 wherein: 
 the detection setting section sets the duty ratio for detection, which is different in duty ration value from the duty ratio for feedback used by the pulse signal generating section before the duty ratio setting section switches over from the feedback setting section to the detection setting section; and 
 based on the natural vibration frequency detected, the drive frequency setting section sets the drive frequency so as not to generate resonance. 
 
     
     
       2. The load drive control device according to  claim 1 , wherein:
 the natural vibration frequency setting section differentiates the detected actual current value to acquire a peak time point of the detected actual current value; and 
 the natural vibration frequency setting section calculates the natural vibration frequency from a plurality of the peak time points. 
 
     
     
       3. The load drive control device according to  claim 1 , wherein:
 under a situation where the target current value is constant, when a predetermined time has elapsed since the target current value became constant, the selection section selects the detection setting section for a predetermined time period. 
 
     
     
       4. The load drive control device according to  claim 3 , wherein
 when the target current value changes after the selection section switches the duty ratio setting section to the detection setting section, the selection section switches the duty ratio setting section to the feedback setting section even before the predetermined time period has elapsed. 
 
     
     
       5. The load drive control device according to  claim 1 , wherein
 the inductive load is a solenoid of a hydraulic valve.